Field of the Invention
This invention is in the field of medical devices to monitor blood pressure, blood oxygen levels, and obtain electrocardiograms. In particular the invention is in the field of handheld medical device designed for easy use by unskilled or semi-skilled patients and healthcare professionals.
Description of the Related Art
The human cardiovascular system is a complex system involving the heart, lungs, arteries, veins and other body components. The human heart itself can be viewed as an electrically triggered four-chamber pump. The right atrium receives deoxygenated blood (generally more blue in color) from the veins, passes the blood to the right ventricle, where the blood is pumped to the lungs. At the lungs, the blood becomes oxygenated (and also changes to a red color depending upon how much oxygen has been absorbed).
The left atrium receives oxygenated blood from the lungs, and passes this oxygenated blood to the left ventricle, which in turn sends oxygenated blood to the body via various arteries. During each heartbeat, usually in response to various electrical pulses (which can be monitored using electrodes and electrocardiogram type methods) various pulsatile sounds are generated (called Korotkoff sounds when used in a cuff-type blood pressure monitoring context), and various pulsatile changes in blood pressure also occur. For example, when the left ventricle is pushing oxygenated blood to the body, blood pressure is higher (systolic blood pressure), and in between heartbeats, when the heart is momentarily resting, the blood pressure is lower (diastolic blood pressure), and these pressure measurements vary according to the patient's pulse rate (typically between about 30 to 200 times per minute).
Various medical abnormalities can alter this process. For example, some medical conditions may cause the heart to beat irregularly (cardiac arrhythmia), and such cardiac arrhythmias are often of high medical concern. Blood pressure may be too high or too low. Due to either cardiac problems, lung problems, or a combination of the two, blood may not be sufficiently oxygenated as it passes through the lungs. Indeed in some diseases, such as chronic obstructive pulmonary disease (COPD), all aspects of the cardiovascular system may be gravely damaged.
Not surprisingly, given how fundamental a well performing cardiovascular system is to human health, various methods of monitoring different aspects of the human cardiovascular system have been developed.
Thus if a heart is receiving abnormal electrical signals, which can be diagnosed by electrodes and electrocardiographic (ECG) methods, the heart muscle may contract abnormally. This abnormal heart muscle contraction may in turn generate an abnormal pulse with characteristic sounds and characteristic changes in blood pressure. These pulse signals may be monitored by traditional sphygmomanometer type blood pressure monitors, which apply pressure to a portion of the body, and monitor the Korotkoff sounds with a stethoscope as a function of the amount of applied pressure. The pulse signals may also be monitored by more recently developed oscillometric methods, where oscillating pressure measurements at various cuff pressure levels can be automatically analyzed according to various algorithms, and pulse results produced. The variation in blood color (light absorption spectra) as a function of blood oxygen levels (saturation) can also be monitored by various types of pulse oximeter measurements.
Previous work in these fields includes Uemura, U.S. Pat. Nos. 4,262,674 and 4,484,584; Taniguchi, U.S. Pat. No. 4,566,464, Shimazu, U.S. Pat. No. 5,680,867, Swearington, U.S. Pat. No. 4,263,918, Amano U.S. Pat. No. 6,095,984, Forstner U.S. Pat. No. 6,485,429, and Muradina, US patent publications 20080077435 and 20120330675; the complete contents of these applications are incorporated herein by reference.
The role of telemedicine in assisting care for COPD was recently reviewed in 2012 article by McLean et. al., (“Telehealthcare for chronic obstructive pulmonary disease (Review)”, The Cochrane Library 2012, issue 8, published by John Wiley & Sons, Ltd).
Methods to derive respiratory rate from pulse oximeter data was discussed by Addison et. al., (“Developing an algorithm for pulse oximetry derived respiratory rate (RRoxi): a healthy volunteer study, J. Clin. Monit. Comput (2012) 26: 45-51), and by Leonard et. al., “Standard pulse oximeters can be used to monitor respiratory rate”, Emerg Med J 2003, 524-525.
Oscillometric methods to measure systolic and diastolic blood pressure were discussed in Babbs, (“Oscillometric measurement of systolic and diastolic blood pressures validated in a physiologic mathematical model”, Biomedical Engineering Online 2012 11;56.)